Due to its electronic properties, germanium is considered to be a replacement for silicon as the semiconductor material of choice to form substrates and/or gate electrodes.
Germanides, e.g. compounds resulting from the reaction between germanium and a metal, such as Ni, are attractive for use in Ge-based integrated circuits to reduce the resistivity of source and drain regions.
However, a fully manufacturable process for germanidation has yet to be developed.
Self-aligned germanides have already been described. Generally, such self-aligned germanides can be formed by depositing a layer of metal over a substrate and a germanium region, heating the structure to form a metal germanide and selectively removing unreacted metal, e.g. using a selective etching technique.
However, the methods that were available before the present invention result in several types of lethal defects, including pits in the Ge and/or the formation of a conductive germanide excrescence (unwanted accretion) over areas intended for isolation.